NATO forces in Afghanistan have launched an investigation after five local policemen were killed in a US air strike during a battle with Taliban insurgents.

Afghan and US troops called for aerial support while fighting in the eastern province of Nangarhar, the US-led NATO coalition said, with local officials reporting special forces were reacting to a Taliban attack on a police post.

"A US aircraft engaged, inadvertently killing five Afghan National Police members and wounding two," said Master Sergeant Bryan Gatewood, a spokesman for NATO's International Security Assistance Force (ISAF).

"An investigation is ongoing to determine additional details of this unfortunate incident."

Two other policemen were wounded in the bungled attack.

The deaths came as the United States attempted to restart stalled talks with president Hamid Karzai's government on the size of a military presence after most international troops leave next year.

Accidental casualties caused by Western air strikes are a major source of friction between Mr Karzai and his international allies.

Afghan security forces do not possess a significant air force, and foreign air power is considered critical to cover the mountainous regions near the Pakistani border, which have long been insurgent hot spots.

But accidental Afghan casualties in air strikes, particularly civilians, infuriate Mr Karzai, and he has previously ordered a ban on his troops calling them in.